Heater tube assembly



May 24, 1966 -rm 3,253,243

HEATER TUBE ASSEMBLY Filed Aug. '7, 1961 IN V EN TOR.

JAMES M. MARTIN ATTORNEYS United States Patent 3,253,243 HEATER TUBE ASSEMBLY James M. Martin, Mason, Mich., assignor, by mesne assignments, to Insto-Gas Corporation, Detroit, Mich, a corporation of Michigan Filed Aug. 7, 1961, Ser. No. 129,675 Claims. (Cl. 338316) This invention relates to heaters and refers more particularly to electric heater tube assemblies.

One object of the invention is to provide a good, reliable connection between a lead or contact and the end of the heating element in an electrical heater tube assembly.

Another object is to provide an electrically non-conductive plug for supporting the lead or contact, of improved construction.

Another object is to provide an electrically non-conductive plug constructed to permit the flow of air in and out of the tube past the lead or contact.

Another object is to provide an electrically non-conductive plug formed to prevent accidental grounding of the heater element to the frame of the heater.

Another object is to provide a heater tube assembly comprising an elongated tube of glass or like material, an electric heating element within the tube, electrically non-conductive plugs at each end of the tube, and an electric contact or lead extending into the tube freely through a passage in the plug and connected to the heating element, the lead having means engaging the plug to hold it on the end of the tube, and the plug being otherwise free of attachment to the tube.

Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is an elevational view of an electric heater tube assembly embodying my invention.

FIGURE 2 is an enlarged fragmentary sectional view of a portion of the heater tube assembly shown in FIG- URE 1.

FIGURE 3 is an enlarged fragmentary clevational View of a portion of the heater tube assembly.

FIGURE 4 is a sectional view of a portion of the heater tube assembly shown in FIGURE 2, seen from a different angle.

FIGURE 5 is a view looking in the direction of the arrow 5 in FIGURE 3.

Referring now more particularly to the drawings, the heater tube assembly is generally indicated at and comprises an elongated cylindrical tube 12 of glass or like non-conductive material, open at both ends. Extending within the tube is an electric heating element 14 which is in the form of an elongated helical wire coil formed of a suitable electrically conductive material such, for example, as resistance wire. The heating element 14 is, of course, resilient and can be stretched in the direction of its length.

At each end of the tube there is a lead or contact 16 .and acontact supporting plug 1 8. Since the lead and plug at one end of the tube are exactly the same as those at th'e other, it will be sufiicient to describe the pair at one efid only, As seen in FIGURES ,.5 the lead 16 is in the forhiofla thin, flat metal strip forked at the outer end as indicatedat 20 for connection to a suitable terminal 22 of a metal housing 24. At its inner end, the contact or lead 16 has a tab extension 26 which is of reduced width, as shown in FIGURES 2 and 4, and is return bent or folded on itself. The return-bent end of the tab extension is secured on itself by a weld 30. An end 32 of the wire coil heating element 14 explace.

3,253,243 Patented May 24, 1966 tends within the fold of the return-bent tab and is securely held by friction.

The plug 18 is formed of any suitable electrically non-conductive material, preferably a ceramic. The plug '18 has a body 34 which includes a circular rim portion 36 and a narrow portion 38 extending axially outwardly from the mid region of the rim. At its inner end, the body 34 has an axial extension or boss 40 which is of somewhat smaller diameter than the inside of the tube. Boss 40 extends loosely within the tube and acts as a pilot. A radial annular shoulder 42 on the inner end of the plug body extends outwardly from. the boss and engages the end of the tube. The plug 18 is otherwise free of connection with the tube.

The plug is formed with an axial passage 44 which extends from the outer end of the body through the portions 34 and 36 thereof and also through the boss 40. As seen in FIGURE 5, the passage is generally rectangular throughout its length, being relatively narrow in comparison with its width. The intermediate portion 46 of the passage is of increased breadth. The width of the passage is only slightly greater than the width of contact 16, and its breadth, beyond the intermediate portion 46, is only slightly greater than the thickness of the contact 16. Accordingly the contact 16 is closely confined within the passage 44 but is capable of axial sliding movement.

The contact 16 is formed with two axially spaced holes 48 and 50. A pin 52 extends through and is permanently secured in hole 50, projecting beyond either side of the contact .16, as seen in FIGURE 5.

The body 34 of the plug 18 is formed with a generally rectangular recess 54 which is narrow in comparison with its width and extends across the passage 44 at the mid point of the passage so that the end portions of the recess lie on opposite sides of the passage. The width dimension of the recess is at right angles to the width dimension of the passage.

Pin 52 is adapted to be received in the recess 54 and to seat against the bottom of the recess as shown in FIGURES 2 and 3.

The heater tube is assembled by securing the pin 52 in the hole 50 of one contact or lead 16, inserting the contact through the passage of a plug 18 to seat the pin in recess 54, and frictionally securing an end of the heating element 14 to the tab 26 of the contact by folding the tab on itself and welding at 30. The other contact 16 is likewise connected to the other end of the heating element 14 by folding its tab over the end of the heating element and welding. Then a long wire is hooked through the hole 48 of the second contact to draw the contact and heating element through the tube and to locate the first assembled contact and plug in position on the end of the tube, as shown in FIGURE 2. Thereafter, and while the second contact is held by the wire, the second plug is sleeved over the second contact and a pin 52 is inserted in the hole 50 and secured in In the assembled relation of the parts, the heating element 14 is under a slight tension to hold the plugs against the ends of the tube. The plugs are not affixed to the tube ends but are merely held by the tension of the heating element.

When the tube assembly is inserted in the metal housing 24, the forked ends of the contacts are rigidly aflixed to the terminals 22 of the integral parts 60 and 62 of the housing. The coefiicient of thermal expansion of the tube 12 is low in comparison with that of the metal housing 24. Hence as the tube assembly 10 heats up, the temperature of the housing 24 will likewise increase and the housing, due to the difference in coeflicients, will expand to a greater deg-rec than the tube. Hence the terminals 22 will tend to separate or move apart a distance greater than the elongation of tube 12. However by reason of the fact that the contacts 16 can move independently of the plugs and tube 12, the contacts can expand with the terminals 22.

By reason of the enlargement 46 of the plug passage 44, clearance is provided for the flow of air into and out of the tube between the walls of the enlargement and the sides of the contact.

What I claim as my invention is:

1. An electric heater tube assembly comprising an elongated heater tube, an elongated, stretchable, resilient heating element within said tube, an electrically nonconductive plug at one end of said tube having a body provided at its inner end with a reduced extension projecting within said one end of said tube, said body having a shoulder at its inner end surrounding said extension and abutting said one end of said tube, said body being otherwise free of connection with said tube, said body having a through passage extending from end to end thereof and communicating with the inside of said tube, said passage being generally rectangular and relatively narrow as compared to its width, a fiat electrical contact extending freely through said passage into said tube and connected to one end of said heating element, a generally rectangular recess in the outer end of said plug extending toward but terminating short of the inner end of said plug, said recess extending across said passage, having portions on opposite sides of said passage, and having its width dimension at right angles to the width dimension of said passage, said contact having members on opposite sides thereof received in said respective recess portions and engaging the bottoms thereof to lim-it inward movement of said contact, and means including a second contact connected to the other end of said heating element to anchor the same against movement toward said plug, thereby to hold said plug in assembly at said one end of said tube.

2. The assembly defined in claim 1, wherein said means includes a second plug of exactly the same construction as the first-mentioned plug bearing the same relationship to the other end of the tube as the first-mentioned plug bears to said one end of the tube and wherein said second contact is of exactly the same construction as the firstmentioned contact and bears the same relationship to the second plug as said first-mentioned contact bears to the first-mentioned plug.

3. The assembly defined in claim 2, wherein the mid region of the passage in each plug is of increased breadth from end to end for the flow of air to and from said tube past the contact therein.

4. An electric heater tube assembly comprising an elongated heater tube, an elongated resilient electric heating element within said tube, an electrically nonconductive plug at one end of said tube having a body provided at its inner end with a reduced extension projecting within said one end of said tube, said body having a shoulder at its inner end abutting said one end of said tube, said body being otherwise free of connection with 4 I said tube, said body having a passage extending from end to end there-of and communicating with the inside of said tube, an electrical contactextending freely through said passage into said tube and connected to one end of said heating element, a recess in the outer end of said plug extending toward but terminating short of the inner end of said plug, said recess extending across said pas-sage and having portions on opposite sides of said passage, said contact having means received in said respective recessed portions and engaging the bottoms thereof to limit inward movement of said contact, and means including a second contact connected to the other end of said heating element to anchor the same against movement toward said plug and to hold said plug at said one end of said tube.

5. In an electric heater tube assembly, an elongated tube of non-conducting material, plugs of non-conducting material having portions abutting opposite ends of said tube, each of said plugs having an axial passage extending therethrough and having a relatively narrow recess extending across each passage, an elongated electric heating element within and extending longitudinally of said tube, an elongated electrical contact extending freely through each of said passages and having its inner end connected to an end of said heating element, and means carried by said elongated electrical contacts and engageable with the inner ends of said recesses, including pins extending transversely of said elongated electrical contacts and disposed one within each of said recesses to relation with opposite ends of said tube.

References Cited by the Examiner UNITED STATES PATENTS 994,447 6/1911 Egly 338-316 X 1,318,029 10/1919 Thomson 338-226 1,563,812 12/1925 Waller 338-329 2,069,348 2/1937 Young 338-332 X 2,276,842 3/1942 Harrison 339-51 2,596,837 5/1952 Calvert 338-233 2,618,676 11/1952 Howard 339-51 2,658,984 11/1953 Mohn 338-226 2,690,491 9/1954 Calvert 338-236 2,831,950 4/1958 Lefebvre 338-226 2,844,694 7/1958 Lefebvre 338-236 2,927,299 3/1960 Lefebvre 338-268 X 2,995,646 8/1961 Kawalle 219-544 X 3,008,030 11/1961 Stanford et al. 338-316 X FOREIGN PATENTS 542,434 1/ 1932 Germany. 62,892 9/ 1940 Norway.

RICHARD M. WOOD, Primary Examiner.

RAY K. WINDHAM, Examiner.

V. Y. MAYEWSKY, H. T. POWELL,

Assistant Examiners. 

5. IN AN ELECTRIC HEATER TUBE ASSEMBLY, AN ELONGATED TUBE OF NON-CONDUCTING MATERIAL, PLUG OF NON-CONDUCTING MATERIAL HAVING PORTIONS ABUTTING OPPOSITE ENDS OF SAID TUBE, EACH OF SAID PLUGS HAVING AN AXIAL PASSAGE EXTENDING THROUGHOUT AND HAVING A RELATIVELY NARROW RECESS EXTENDING ACROSS EACH PASSAGE, AN ELONGATED ELECTRIC HEATING ELEMENT WITHIN AND EXTENDING LONGITUDINALLY OF SAID TUBE, AN ELONGATED ELECTRICAL CONTACT EXTENDING FREELY THROUGH EACH OF SAID PASSAGES AND HAVING ITS INNER END CONNECTED TO AN END OF SAID HEATING ELEMENT, AND MEANS CARRIED BY SAID ELONGATED ELECTRICAL CONTACTS AND ENGAGEABLE WITH THE INNER ENDS OF RECESSES, INCLUDING PINS EXTENDING TRANSVERSELY OF SAID ELONGATED ELECTRICAL CONTACTS AND DISPOSED ONE WITHIN EACH OF SAID RECESSES TO HOLD THE PORTIONS AFORESAID OF SAID PLUGS IN ABUTTING RELATION WITH OPPOSITE ENDS OF SAID TUBE. 